"Until oil consumption stabilizes..."

[flyingcheesehead]

OK, so explain what this really means, and when break-in is really over.

We have two airplanes on break-in right now. One has had what might be called "unstable" oil consumption, with 3-4 flights not requiring any, followed by a flight that'll take a couple of quarts.

The other one was run first by Poplar Grove Airmotive in their test cell for ~3 hours before being put on the plane. It has used only one quart in over 20 hours since it was hung on the airplane.

Does that mean it's done? Does that mean we didn't really need to break it in beyond what PGA did, or can rings "loosen" again if the engine isn't run hard for a longer period?

Back to the first airplane, how many hours should the oil consumption be "stable" (and please define stable) before we stop using the break-in procedures?

 

[RotorAndWing]

Stable is when the cylinder head and oil temps stabilize as well as oil consumption is in the neighborhood of 1 quart every 8 to 10 hours.

Different factors arise with different cylinders. If your one plane has chrome cylinders or steel nitride will make a big difference on break in times. The fellow on this board from Zepherhills Aircraft Engines can give a better dissertation on cylinders.

On flying club aircraft versus single owner it can be a little difficult to track oil consumption due to those that insist when the oil is slightly low dumping in a whole quart, then blowing most of it out the breather tube and skewing the oil onsumption numbers.

When I had my helicopter school if we installed an overhauled engine it was our practice for the first 10 hours to have only company pilots fly the ship with no students or rentals. Helicopter engines break in faster since they are running at high power settings constantly.

 

[poadeleted20]

To expand on one of R&W's comments, you should expect the engine to run a bit hotter initially (especially CHT) due to the friction of the rings and cylinder walls grinding themselves to a smooth fit. As the fit is achieved, the friction goes away and temps drop and then stabilize at a lower value than first seen. You'll probably see more change in CHT than in oil temp on this.

 

[tonycondon]

give it a couple thousand hours. then it should be just about right...

 

[Let'sgoflying!]

give it a couple thousand hours. then it should be just about right...

Most don't barely get broken in then an AD pops up requiring you to change them.

What type of cylinders are these? New steel or ?

 

[flyingcheesehead]

Plane 1: 1977 Archer II (Lyc O-360-A4M) with factory instrumentation. No CHT gauge at all.

I believe they are used overhauled Lyc factory cylinders. The Superiors they replaced had all cracked in a similar fashion (starting at the exhaust valve), engine is around 1600 SMOH. A&P's said they were similar to some AD'ed cylinders, but not subject to the AD though the problem was the same (similar to the more recent ECI AD's).

So on this one, we should just wait for the 1 quart each 8-10 hours and call it done?

Plane 2: 1971 C182 (TCM O-470-R) with factory instrumentation plus a JPI EDM 700 installed at the recent overhaul.

This one has the instrumentation, but I don't really know what I'm looking for. The #2 and #3 cylinders seem to run the hottest and will occasionally set off the 400 CHT warning (that's how I set up the JPI). I haven't gotten the hang of leaning it out *just so* as it seems after I lean it, close the cowl flaps, etc. it'll start yelling about one of those two cylinders within 5 minutes or so. Of course, I haven't flown it in 6 weeks so it's probably had 10 hours on it since then and may not be doing that any more.

The oil, like I said, has been VERY steady the whole way. 1 quart/10 hours would take us all the way back to day 1!

This one, we could call finished based on oil consumption alone - Should I see if it's still got those two cylinders running hot? Or could that simply be that I'm just not leaning it quite right with the new gadget?

 

[poadeleted20]

Plane 2: 1971 C182 (TCM O-470-R) with factory instrumentation plus a JPI EDM 700 installed at the recent overhaul.

This one has the instrumentation, but I don't really know what I'm looking for.

You're looking to see what the CHT's were for all four cylinders right after level-off on the first flight. Then you want to see if they decline and stabililze at a lower lever later on. Data download and analysis with the EZ software is helpful.